An optical fiber composite electric power cable is a composite cable where an optical fiber is included in an electric power cable. The optical fiber composite electric power cable is widely used under installation environments that require monitoring of the operation of electricity, since temperature distribution of the cable may be detected using optical fibers.
Generally, the optical fiber composite electric power cable includes a conductor 10 provided at the center of the cable as shown in FIG. 1, and an inner semiconductive layer 11, an isolative layer 12, an outer semiconductive layer 13, a shielding layer 17 and a corrosion-protective layer 18 are subsequently provided around the conductor 10. In particular, adjacent to the shielding layer 17, a filling material 15 such as jelly compound and silicon oil are filled around the shielding layer 17, and an optical fiber unit 14 surrounded by a protective tube 16 is also arranged thereto. More specifically, Japanese Laid-open Publication No. 1990-144810 discloses an optical fiber composite electric power cable in which an optical fiber is arranged to the shielding layer 17 or the corrosion-protective layer 18, and Japanese Laid-open Publication Nos. 1994-148001, 1994-181013, 1994-181014 and 1994-181015 disclose an electric power cable in which an optical fiber is arranged in a part of the shielding layer 17 in a length direction and a method for measuring temperature distribution. In addition, U.S. Pat. No. 4,867,527 discloses an optical fiber composite electric power cable provided with an optical fiber out of the shielding layer 17 of the electric power cable and in which the optical fiber protective layer 16 is inserted.
However, when installing the conventional optical fiber composite electric power cable as mentioned above, an optical fiber connection box should be added in a limited space of an electric power cable connection box, which makes the installation work difficult. In addition, since such an optical fiber connection box 21 should be provided to each electric power cable connection box 20, which is installed in every 300 m region as shown in FIG. 2, optical loss is very significant.
Meanwhile, it is also possible to draw an optical fiber out of the electric power cable connection box 20 and then configure the optical fiber connection box separately in order to ensure a space for the optical fiber connection box, but this may make the electric power cable connection box 20 more complicated.